P125 - TLR4 ACTIVATION UPREGULATES EXPRESSION OF OXIDATIVE ENZYMES: IMPLICATIONS FOR INTESTINAL TUMORIGENESIS AND LUMINAL MICROBIOTA
(Room Poster Hall)
19 Jan 18
5:30 PM
-
7:00 PM
Tracks:
Clinical and Research Challenges
Background: overexpression of Dual oxidase 2 (Duox2) occurs as an early event in both human inflammatory bowel disease and mouse models of colitis, and has been associated with dysbiosis. We have previously shown that mice bearing constitutive activation of toll-like receptor 4 (TLR4) in intestinal epithelial cells (IECs) (villin-TLR4) have altered microbial populations, increased cytokine expression, and increased Nox1 and Duox2 expression. Villin-TLR4 mice develop spontaneous duodenal tumors. Here, we test whether TLR4-mediated induction of Nox1 and Duox2 is dependent on luminal microbiota. Methods: villin-TLR4 mice were treated or not with a combination of antibiotics for 4 weeks to deplete their microflora. IECs from duodenum and colon segments were isolated, as well as spontaneous tumors occurring in duodenum. Duodenum and colon organoids from wild type (WT) and TLR4-/- mice were stimulated with lipopolysaccharide (LPS) and/or TNF and IFN-γ. Nox1 and Duox2 expression was evaluated in all samples by quantitative PCR. Results: Antibiotic treatment caused a marked depletion of bacterial populations in stool. Depletion of microflora decreased expression of Nox1 and Duox2 in villin-TLR4 duodenum but not in tumors or colon tissue. Even after antibiotic treatment, villin-TLR4 mice continued to have significantly elevated Nox-1 and Duox-2 expression in the duodenum and colon when compared to their untreated littermates. To further investigate whether TLR4 signaling is responsible for induction of Nox-1 and Duox-2, WT or TLR4-/- duodenum and colon organoids were treated with ultrapure LPS. This resulted in significant upregulation of Nox-1 and Duox-2 in WT but not TLR4-/- organoids. No increased expression was seen with TNF+IFN-g. Conclusions: TLR4 drives expression of oxidative enzymes in the intestine. LPS and luminal microbiota increase expression of Nox-1/Duox-2. We speculate that these oxidative pathways participate in TLR4-dependent neoplasia of the intestine.